

async function levelOne(value, callback)
{
    var newScore = value + 5;
    callback(newScore);
}

async function startGame(str, arr, callback) {
  const num = str + arr + 5;
  let results = ''
  console.log('result: ' + num);
    
  // levelOne()的第二个参数为回调函数
  levelOne(num, function(levelOneReturnedValue) {
    results = levelOneReturnedValue
  }, function(err) {
    if (err) return callback(err);
    return callback(results)
  });
}

startGame(1,2);